Freezing the sperm of all 18-year-old men should be considered because of the risks of having children in later life, a British expert has claimed.

Kevin Smith, from Abertay University in Dundee, said sperm becomes more prone to mutations with age, increasing the risk of genetic disorders.

He said state-funded universal sperm-banking "offers a straightforward solution", but another expert at the University of Sheffield branded the idea "simply crackers".

In a paper in the Journal of Medical Ethics, Dr Smith said he was not claiming that children from older fathers were "worse off" but they more likely to suffer from genetic diseases.

"In principle, it would be straightforward for young men (aged perhaps 18) to elect to have their sperm stored until starting a family at an older age, thus avoiding a build-up of new mutations," he wrote.

"Sperm banking offers a straightforward solution to the problem of paternal age effect genetic disease."

Dr Smith, a bioethicist at the university's school of science, engineering and technology, said the technology for storing sperm was "well-established" and the "widespread adoption" of all young men would be "desirable".

"This approach may appear radical or intuitively unwelcome to some, in that it would entail a wholescale move away from natural conception," he added.

"Sperm banking is a practical solution that could in principle be implemented immediately.

"It would provide an ethically unproblematic way for individuals to opt for deferred fatherhood."

Allan Pacey, a professor of andrology at the University of Sheffield, said: "This is one of the most ridiculous suggestions I have heard in a long time.

"The idea that mass sperm banking for 18-year-olds should be funded by the NHS is simply crackers, in my opinion.

"We know that the sperm from the majority of men won't freeze very well, which is one of the reasons why sperm donors are in short supply.

"Therefore, men who froze their sperm at 18, and returned to use it later in life, would essentially be asking their wives to undergo one or more IVF procedures in order to start a family."

Prof Pacey said that, while there was evidence linking some genetic disorders to the age of the father, the risks are "really quite small" and are most likely to affect men aged over 45.

The average age of fatherhood in England and Wales increased from 31 in the early 1990s to nearly 33 by 2013, according to the Office for National Statistics.

Professor Adam Balen, chairman of the British Fertility Society, said: " This move would provide a very artificial approach to having babies. Procreation should not be taken out of the bedroom and into the test-tube unless there are defined fertility problems.

"There should be a greater focus in the UK on supporting young couples to establish their careers and relationships and be supported in having children at a young age before the natural decline in both female and male fertility.

"There is a need for better education of youngsters so that they are informed about the implications of delaying starting a family and at the same time improved societal support for working mothers and fathers with better childcare facilities to enable couples to establish careers and families."